Eccrine sweat glands in surgical skin biopsies from normal children and patients afflicted with pancreatic cystic fibrosis are studied and compared. Cytochemical, and electron microscopic techniques are used to study the localization of specific enzymes and the sites of synthesis and fate of glycoproteins and mucopolysaccharides. Routine electron microscopy of each case available provides information on cell types affected by the disease and alterations in duct and secretory segments of the sweat glands. Consistent findings in accumulated data are correlated with other biochemical and physiological observations. Studies on other model systems involving cation secretion are effected on the nasal glands of reptiles and birds.